A four‐coil structure wireless power transfer system with constant current and constant voltage charging: Analysis, design, and experiment

Abstract

AbstractWireless power transfer (WPT) technology can transmit power through high‐frequency magnetic fields, which is safer and more flexible than conventional conductive charging method. The WPT systems for charging lithium batteries need to meet the charging function of first constant current (CC) and then constant voltage (CV). In addition, to avoid reactive power loss, the input impedance of the system is preferably purely resistive, that is, to meet the zero phase angle (ZPA) condition. In view of the above problems, this paper proposes a four‐coil structure WPT system based on dual‐frequency switching method to realize load‐independent CC and CV charging outputs at two fixed ZPA frequency points, respectively. It is worth noting that there is only one compensation capacitor on the receiving side, which ensures the compactness and portability of the receiving side of the WPT system. An experimental prototype with charging current of 2.2 A in CC mode and charging voltage of 28 V in CV mode is established to verify the correctness and practicality of the proposed four‐coil structure WPT system. The experimental results are basically in good agreement with the theoretical analysis.